Wafer chucking system for advanced plasma ion energy processing systems

ABSTRACT

Systems, methods and apparatus for regulating ion energies in a plasma chamber and chucking a substrate to a substrate support are disclosed. An exemplary method includes placing a substrate in a plasma chamber, forming a plasma in the plasma chamber, controllably switching power to the substrate so as to apply a periodic voltage function to the substrate, and modulating, over multiple cycles of the periodic voltage function, the periodic voltage function responsive to a desired distribution of energies of ions at the surface of the substrate so as to effectuate the desired distribution of ion energies on a time-averaged basis.

RELATED CASES AND PRIORITY

This application claims the benefit of Non-Provisional U.S. patentapplication Ser. No. 12/870,837 filed on Aug. 29, 2010. The details ofapplication Ser. No. 12/870,837 are incorporated by reference into thepresent application in their entirety and for all proper purposes.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to plasma processing. Inparticular, but not by way of limitation, the present invention relatesto methods and apparatuses for plasma-assisted etching and/ordeposition.

BACKGROUND OF THE DISCLOSURE

Many types of semiconductor devices are fabricated using plasma-basedetching techniques. If it is a conductor that is etched, a negativevoltage with respect to ground may be applied to the conductivesubstrate so as to create a substantially uniform negative voltageacross the surface of the substrate conductor, which attracts positivelycharged ions toward the conductor, and as a consequence, the positiveions that impact the conductor have substantially the same energy.

If the substrate is a dielectric, however, a non-varying voltage isineffective to place a voltage across the surface of the substrate. Butan AC voltage (e.g., high frequency) may be applied to the conductiveplate (or chuck) so that the AC field induces a voltage on the surfaceof the substrate. During the positive half of the AC cycle, thesubstrate attracts electrons, which are light relative to the mass ofthe positive ions; thus many electrons will be attracted to the surfaceof the substrate during the positive part of the cycle. As aconsequence, the surface of the substrate will be charged negatively,which causes ions to be attracted toward the negatively-charged surface.And when the ions impact the surface of the substrate, the impactdislodges material from the surface of the substrate—effectuating theetching.

In many instances, it is desirable to have a narrow ion energydistribution, but applying a sinusoidal waveform to the substrateinduces a broad distribution of ion energies, which limits the abilityof the plasma process to carry out a desired etch profile. Knowntechniques to achieve a narrow ion energy distribution are expensive,inefficient, difficult to control, and may adversely affect the plasmadensity. As a consequence, these known techniques have not beencommercially adopted. Accordingly, a system and method are needed toaddress the shortfalls of present technology and to provide other newand innovative features.

SUMMARY

Illustrative embodiments of the present disclosure that are shown in thedrawings are summarized below. These and other embodiments are morefully described in the Detailed Description section. It is to beunderstood, however, that there is no intention to limit the inventionto the forms described in this Summary of the Invention or in theDetailed Description. One skilled in the art can recognize that thereare numerous modifications, equivalents, and alternative constructionsthat fall within the spirit and scope of the invention as expressed inthe claims.

According to one embodiment, the invention may be characterized as asystem for plasma-based processing. The system in this embodimentincludes a plasma processing chamber configured to contain a plasma anda substrate support positioned within the plasma processing chamber thatis disposed to support a substrate. In addition, an ion-energy controlportion provides at least one ion-energy control signal responsive to atleast one ion-energy distribution setting that is indicative of adesired ion energy distribution at the surface of the substrate. Aswitch-mode power supply applies power to the substrate to effectuatethe desired ion energy distribution at the surface of the substrate, andan ion current compensation component in this embodiment provides acontrollable width of the ion energy distribution.

According to another embodiment, the invention may be described as amethod for plasma-based processing that includes controllably switchingpower to the substrate so as to apply a periodic voltage function to thesubstrate and modulating, over multiple cycles of the periodic voltagefunction, the periodic voltage function responsive to a desired ionenergy distribution at the surface of the substrate so as to effectuatethe desired ion energy distribution on a time-averaged basis.

According to yet another embodiment, the invention may be characterizedas a plasma-based processing apparatus that includes a switch-mode powersupply configured to apply a periodic voltage function and an ion-energycontrol portion that modulates, over multiple cycles of the periodicvoltage function, at least one parameter of the periodic voltagefunction responsive to at least one ion-energy distribution setting thatis indicative of a desired ion energy distribution at the surface of thesubstrate.

These and other embodiments are described in further detail herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects and advantages and a more complete understanding of thepresent invention are apparent and more readily appreciated by referenceto the following Detailed Description and to the appended claims whentaken in conjunction with the accompanying Drawings where like orsimilar elements are designated with identical reference numeralsthroughout the several views and wherein:

FIG. 1 illustrates a block diagram of a plasma processing system inaccordance with one implementation of the present invention;

FIG. 2 is a block diagram depicting an exemplary embodiment of theswitch-mode power system depicted in FIG. 1;

FIG. 3 is a schematic representation of components that may be utilizedto realize the switch-mode bias supply described with reference to FIG.2;

FIG. 4 is a timing diagram depicting two drive signal waveforms;

FIG. 5 is a graphical representation of a single mode of operating theswitch mode bias supply, which effectuates an ion energy distributionthat is concentrated at a particular ion energy;

FIG. 6 are graphs depicting a bi-modal mode of operation in which twoseparate peaks in ion energy distribution are generated;

FIGS. 7A and 7B are is are graphs depicting actual, direct ion energymeasurements made in a plasma;

FIG. 8 is a block diagram depicting another embodiment of the presentinvention;

FIG. 9A is a graph depicting an exemplary periodic voltage function thatis modulated by a sinusoidal modulating function;

FIG. 9B is an exploded view of a portion of the periodic voltagefunction that is depicted in FIG. 9A;

FIG. 9C depicts the resulting distribution of ion energies, ontime-averaged basis, that results from the sinusoidal modulation of theperiodic voltage function;

FIG. 9D depicts actual, direct, ion energy measurements made in a plasmaof a resultant, time averaged, IEDF when a periodic voltage function ismodulated by a sinusoidal modulating function;

FIG. 10A depicts a periodic voltage function is modulated by a sawtoothmodulating function;

FIG. 10B is an exploded view of a portion of the periodic voltagefunction that is depicted in FIG. 10A;

FIG. 10C is a graph depicting the resulting distribution of ionenergies, on a time averaged basis, that results from the sinusoidalmodulation of the periodic voltage function in FIGS. 10A and 10B;

FIG. 11 are graphs showing IEDF functions in the right column andassociated modulating functions in the left column;

FIG. 12 is a block diagram depicting an embodiment in which an ioncurrent compensation component compensates for ion current in a plasmachamber;

FIG. 13 is a diagram depicting an exemplary ion current compensationcomponent;

FIG. 14 is a graph depicting an exemplary voltage at node Vo depicted inFIG. 13;

FIGS. 15A-15C are voltage waveforms as appearing at the surface of thesubstrate or wafer responsive to compensation current;

FIG. 16 is an exemplary embodiment of a current source, which may beimplemented to realize the current source described with reference toFIG. 13;

FIGS. 17A and 17B are block diagrams depicting other embodiments of thepresent invention;

FIG. 18 is a block diagram depicting yet another embodiment of thepresent invention;

FIG. 19 is a block diagram depicting still another embodiment of thepresent invention;

FIG. 20 is a block diagram input parameters and control outputs that maybe utilized in connection with the embodiments described with referenceto FIGS. 1-19;

FIG. 21 is a block diagram depicting yet another embodiment of thepresent invention;

FIG. 22 is a block diagram depicting yet another embodiment of thepresent invention;

FIG. 23 is a block diagram depicting yet another embodiment of thepresent invention;

FIG. 24 is a block diagram depicting yet another embodiment of thepresent invention;

FIG. 25 is a block diagram depicting yet another embodiment of thepresent invention;

FIG. 26 is a block diagram depicting yet another embodiment of thepresent invention;

FIG. 27 is a block diagram depicting yet another embodiment of thepresent invention;

FIG. 28 illustrates a method according to an embodiment of thisdisclosure; and

FIG. 29 illustrates another method according to an embodiment of thisdisclosure.

DETAILED DESCRIPTION

An exemplary embodiment of a plasma processing system is shown generallyin FIG. 1. As depicted, a plasma power supply 102 is coupled to a plasmaprocessing chamber 104 and a switch-mode power supply 106 is coupled toa support 108 upon which a substrate 110 rests within the chamber 104.Also shown is a controller 112 that is coupled to the switch-mode powersupply 106.

In this exemplary embodiment, the plasma processing chamber 104 may berealized by chambers of substantially conventional construction (e.g.,including a vacuum enclosure which is evacuated by a pump or pumps (notshown)). And, as one of ordinary skill in the art will appreciate, theplasma excitation in the chamber 104 may be by any one of a variety ofsources including, for example, a helicon type plasma source, whichincludes magnetic coil and antenna to ignite and sustain a plasma 114 inthe reactor, and a gas inlet may be provided for introduction of a gasinto the chamber 104.

As depicted, the exemplary plasma chamber 104 is arranged and configuredto carry out plasma-assisted etching of materials utilizing energeticion bombardment of the substrate 110. The plasma power supply 102 inthis embodiment is configured to apply power (e.g., RF power) via amatching network (not shown)) at one or more frequencies (e.g., 13.56MHz) to the chamber 104 so as to ignite and sustain the plasma 114. Itshould be understood that the present invention is not limited to anyparticular type of plasma power supply 102 or source to couple power tothe chamber 104, and that a variety of frequencies and power levels maybe may be capacitively or inductively coupled to the plasma 114.

As depicted, a dielectric substrate 110 to be treated (e.g., asemiconductor wafer), is supported at least in part by a support 108that may include a portion of a conventional wafer chuck (e.g., forsemiconductor wafer processing). The support 108 may be formed to havean insulating layer between the support 108 and the substrate 110 withthe substrate 110 being capacitively coupled to the platforms but mayfloat at a different voltage than the support 108.

As discussed above, if the substrate 110 and support 108 are conductors,it is possible to apply a non-varying voltage to the support 108, and asa consequence of electric conduction through the substrate 110, thevoltage that is applied to the support 108 is also applied to thesurface of the substrate 110.

When the substrate 110 is a dielectric, however, the application of anon-varying voltage to the support 108 is ineffective to place a voltageacross the treated surface of the substrate 110. As a consequence, theexemplary switch-mode power supply 106 is configured to be controlled soas to effectuate a voltage on the surface of the substrate 110 that iscapable of attracting ions in the plasma 114 to collide with thesubstrate 110 so as to carry out a controlled etching and/or depositionof the substrate 110.

Moreover, as discussed further herein, embodiments of the switch-modepower supply 106 are configured to operate so that there is aninsubstantial interaction between the power applied (to the plasma 114)by the plasma power supply 102 and the power that is applied to thesubstrate 110 by the switch-mode power supply 106. The power applied bythe switch-mode power supply 106, for example, is controllable so as toenable control of ion energy without substantially affecting the densityof the plasma 114.

Furthermore, many embodiments of the exemplary switch-mode supply 106depicted in FIG. 1 are realized by relatively inexpensive componentsthat may be controlled by relatively simple control algorithms. And ascompared to prior art approaches, many embodiments of the switch modepower supply 106 are much more efficient; thus reducing energy costs andexpensive materials that are associated with removing excess thermalenergy.

One known technique for applying a voltage to a dielectric substrateutilizes a high-power linear amplifier in connection with complicatedcontrol schemes to apply power to a substrate support, which induces avoltage at the surface of the substrate. This technique, however, hasnot been adopted by commercial entities because it has not proven to becost effective nor sufficiently manageable. In particular, the linearamplifier that is utilized is typically large, very expensive,inefficient, and difficult to control. Furthermore, linear amplifiersintrinsically require AC coupling (e.g., a blocking capacitor) andauxiliary functions like chucking are achieved with a parallel feedcircuit which harms AC spectrum purity of the system for sources with achuck.

Another technique that has been considered is to apply high frequencypower (e.g., with one or more linear amplifiers) to the substrate. Thistechnique, however, has been found to adversely affect the plasmadensity because the high frequency power that is applied to thesubstrate affects the plasma density.

In some embodiments, the switch-mode power supply 106 depicted in FIG. 1may be realized by buck, boost, and/or buck-boost type powertechnologies. In these embodiments, the switch-mode power supply 106 maybe controlled to apply varying levels of pulsed power to induce apotential on the surface of the substrate 110.

In other embodiments, the switch-mode power supply 106 is realized byother more sophisticated switch mode power and control technologies.Referring next to FIG. 2, for example, the switch-mode power supplydescribed with reference to FIG. 1 is realized by a switch-mode biassupply 206 that is utilized to apply power to the substrate 110 toeffectuate one or more desired energies of the ions that bombard thesubstrate 110. Also shown are an ion energy control component 220, anarc detection component 222, and a controller 212 that is coupled toboth the switch-mode bias supply 206 and a waveform memory 224.

The illustrated arrangement of these components is logical; thus thecomponents can be combined or further separated in an actualimplementation, and the components can be connected in a variety of wayswithout changing the basic operation of the system. In some embodimentsfor example, the controller 212, which may be realized by hardware,software, firmware, or a combination thereof, may be utilized to controlboth the power supply 202 and switch-mode bias supply 206. Inalternative embodiments, however, the power supply 202 and theswitch-mode bias supply 206 are realized by completely separatedfunctional units. By way of further example, the controller 212,waveform memory 224, ion energy control portion 220 and the switch-modebias supply 206 may be integrated into a single component (e.g.,residing in a common housing) or may be distributed among discretecomponents.

The switch-mode bias supply 206 in this embodiment is generallyconfigured to apply a voltage to the support 208 in a controllablemanner so as to effectuate a desired distribution of the energies ofions bombarding the surface of the substrate. More specifically, theswitch-mode bias supply 206 is configured to effectuate the desireddistribution of ion energies by applying one or more particularwaveforms at particular power levels to the substrate. And moreparticularly, responsive to an input from the ion energy control portion220, the switch-mode bias supply 206 applies particular power levels toeffectuate particular ion energies, and applies the particular powerlevels using one or more voltage waveforms defined by waveform data inthe waveform memory 224. As a consequence, one or more particular ionbombardment energies may be selected with the ion control portion tocarry out controlled etching of the substrate.

As depicted, the switch-mode power supply 206 includes switch components226′, 226″ (e.g., high power field effect transistors) that are adaptedto switch power to the support 208 of the substrate 210 responsive todrive signals from corresponding drive components 228′, 228″. And thedrive signals 230′, 230″ that are generated by the drive components228′, 228″ are controlled by the controller 212 based upon timing thatis defined by the content of the waveform memory 224. For example, thecontroller 212 in many embodiments is adapted to interpret the contentof the waveform memory and generate drive-control signals 232′, 232″,which are utilized by the drive components 228′, 228″ to control thedrive signals 230′, 230″ to the switching components 226′, 226″.Although two switch components 226′, 226″, which may be arranged in ahalf-bridge configuration, are depicted for exemplary purposes, it iscertainly contemplated that fewer or additional switch components may beimplemented in a variety of architectures (e.g., an H-bridgeconfiguration).

In many modes of operation, the controller 212 (e.g., using the waveformdata) modulates the timing of the drive-control signals 232′, 232″ toeffectuate a desired waveform at the support 208 of the substrate 210.In addition, the switch mode bias supply 206 is adapted to supply powerto the substrate 210 based upon an ion-energy control signal 234, whichmay be a DC signal or a time-varying waveform. Thus, the presentembodiment enables control of ion distribution energies by controllingtiming signals to the switching components and controlling the power(controlled by the ion-energy control component 220) that is applied bythe switching components 226′, 226″.

In addition, the controller 212 in this embodiment is configured,responsive to an arc in the plasma chamber 204 being detected by the arcdetection component 222, to carry out arc management functions. In someembodiments, when an arc is detected the controller 212 alters thedrive-control signals 232′, 232″ so that the waveform applied at theoutput 236 of the switch mode bias supply 206 extinguishes arcs in theplasma 214. In other embodiments, the controller 212 extinguishes arcsby simply interrupting the application of drive-control signals 232′,232″ so that the application of power at the output 236 of theswitch-mode bias supply 206 is interrupted.

Referring next to FIG. 3, it is a schematic representation of componentsthat may be utilized to realize the switch-mode bias supply 206described with reference to FIG. 2. As shown, the switching componentsT1 and T2 in this embodiment are arranged in a half-bridge (alsoreferred to as or totem pole) type topology. Collectively, R2, R3, C1,and C2 represent a plasma load, and C3 is an optional physical capacitorto prevent DC current from the voltage induced on the surface of thesubstrate or from the voltage of an electrostatic chuck (not shown) fromflowing through the circuit. As depicted, L1 is stray inductance (e.g.,the natural inductance of the conductor that feeds the power to theload). And in this embodiment, there are three inputs: Vbus, V2, and V4.

V2 and V4 represent drive signals (e.g., the drive signals 230′, 230″output by the drive components 228′, 228″ described with reference toFIG. 2), and in this embodiment, V2 and V4 can be timed (e.g., thelength of the pulses and/or the mutual delay) so that the closure of T1and T2 may be modulated to control the shape of the voltage output atVout, which is applied to the substrate support. In manyimplementations, the transistors used to realize the switchingcomponents T1 and T2 are not ideal switches, so to arrive at a desiredwaveform, the transistor-specific characteristics are taken intoconsideration. In many modes of operation, simply changing the timing ofV2 and V4 enables a desired waveform to be applied at Vout.

For example, the switches T1, T2 may be operated so that the voltage atthe surface of the substrate 110, 210 is generally negative withperiodic voltage pulses approaching and/or slightly exceeding a positivevoltage reference. The value of the voltage at the surface of thesubstrate 110, 210 is what defines the energy of the ions, which may becharacterized in terms of an ion energy distribution function (IEDF). Toeffectuate desired voltage(s) at the surface of the substrate 110, 210,the pulses at Vout may be generally rectangular and have a width that islong enough to induce a brief positive voltage at the surface of thesubstrate 110, 210 so as to attract enough electrons to the surface ofthe substrate 110, 210 in order to achieve the desired voltage(s) andcorresponding ion energies.

Vbus in this embodiment defines the amplitude of the pulses applied toVout, which defines the voltage at the surface of the substrate, and asa consequence, the ion energy. Referring briefly again to FIG. 2, Vbusmay be coupled to the ion energy control portion, which may be realizedby a DC power supply that is adapted to apply a DC signal or atime-varying waveform to Vbus.

The pulse width, pulse shape, and/or mutual delay of the two signals V2,V4 may be modulated to arrive at a desired waveform at Vout, and thevoltage applied to Vbus may affect the characteristics of the pulses. Inother words, the voltage Vbus may affect the pulse width, pulse shapeand/or the relative phase of the signals V2, V4. Referring briefly toFIG. 4, for example, shown is a timing diagram depicting two drivesignal waveforms that may be applied to T1 and T2 (as V2 and V4) so asto generate the period voltage function at Vout as depicted in FIG. 4.To modulate the shape of the pulses at Vout (e.g. to achieve thesmallest time for the pulse at Vout, yet reach a peak value of thepulses) the timing of the two gate drive signals V2, V4 may becontrolled.

For example, the two gate drive signals V2, V4 may be applied to theswitching components T1, T2 so the time that each of the pulses isapplied at Vout may be short compared to the time T between pulses, butlong enough to induce a positive voltage at the surface of the substrate110, 210 to attract electrons to the surface of the substrate 110, 210.Moreover, it has been found that by changing the gate voltage levelbetween the pulses, it is possible to control the slope of the voltagethat is applied to Vout between the pulses (e.g., to achieve asubstantially constant voltage at the surface of the substrate betweenpulses). In some modes of operation, the repetition rate of the gatepulses is about 400 kHz, but this rate may certainly vary fromapplication to application.

Although not required, in practice, based upon modeling and refiningupon actual implementation, waveforms that may be used to generate thedesired ion energy distributions may be defined, and the waveforms canbe stored (e.g., in the waveform memory portion described with referenceto FIG. 1 as a sequence of voltage levels). In addition, in manyimplementations, the waveforms can be generated directly (e.g., withoutfeedback from Vout); thus avoiding the undesirable aspects of a feedbackcontrol system (e.g., settling time).

Referring again to FIG. 3, Vbus can be modulated to control the energyof the ions, and the stored waveforms may be used to control the gatedrive signals V2, V4 to achieve a desired pulse amplitude at Vout whileminimizing the pulse width. Again, this is done in accordance with theparticular characteristics of the transistors, which may be modeled orimplemented and empirically established. Referring to FIG. 5, forexample, shown are graphs depicting Vbus versus time, voltage at thesurface of the substrate 110, 210 versus time, and the corresponding ionenergy distribution.

The graphs in FIG. 5 depict a single mode of operating the switch modebias supply 106, 206, which effectuates an ion energy distribution thatis concentrated at a particular ion energy. As depicted, to effectuatethe single concentration of ion energies in this example, the voltageapplied at Vbus is maintained constant while the voltages applied to V2and V4 are controlled (e.g., using the drive signals depicted in FIG. 3)so as to generate pulses at the output of the switch-mode bias supply106, 206, which effectuates the corresponding ion energy distributionshown in FIG. 5.

As depicted in FIG. 5, the potential at the surface of the substrate110, 210 is generally negative to attract the ions that bombard and etchthe surface of the substrate 110, 210. The periodic short pulses thatare applied to the substrate 110, 210 (by applying pulses to Vout) havea magnitude defined by the potential that is applied to Vbus, and thesepulses cause a brief change in the potential of the substrate 110, 210(e.g., close to positive or slightly positive potential), which attractselectrons to the surface of the substrate to achieve the generallynegative potential along the surface of the substrate 110, 210. Asdepicted in FIG. 5, the constant voltage applied to Vbus effectuates asingle concentration of ion flux at particular ion energy; thus aparticular ion bombardment energy may be selected by simply setting Vbusto a particular potential. In other modes of operation, two or moreseparate concentrations of ion energies may be created.

Referring next to FIG. 6, for example, shown are graphs depicting abi-modal mode of operation in which two separate peaks in ion energydistribution are generated. As shown, in this mode of operation, thesubstrate experiences two distinct levels of voltages and periodicpulses, and as a consequence, two separate concentrations of ionenergies are created. As depicted, to effectuate the two distinct ionenergy concentrations, the voltage that is applied at Vbus alternatesbetween two levels, and each level defines the energy level of the twoion energy concentrations.

Although FIG. 6 depicts the two voltages at the substrate 110, 210 asalternating after every pulse, this is certainly not required. In othermodes of operation for example, the voltages applied to V2 and V4 areswitched (e.g., using the drive signals depicted in FIG. 3) relative tothe voltage applied to Vout so that the induced voltage at surface ofthe substrate alternates from a first voltage to a second voltage (andvice versa) after two or more pulses.

In prior art techniques, attempts have been made to apply thecombination of two waveforms (generated by waveform generators) to alinear amplifier and apply the amplified combination of the twowaveforms to the substrate in order to effectuate multiple ion energies.This approach, however, is much more complex then the approach describedwith reference to FIG. 6, and requires an expensive linear amplifier,and waveform generators.

Referring next to FIGS. 7A and 7B, shown are graphs depicting actual,direct ion energy measurements made in a plasma corresponding tomonoenergetic and dual-level regulation of the DC voltage applied toVbus, respectively. As depicted in FIG. 7A, the ion energy distributionis concentrated around 80 eV responsive to a non-varying application ofa voltage to Vbus (e.g., as depicted in FIG. 5). And in FIG. 7B, twoseparate concentrations of ion energies are present at around 85 eV and115 eV responsive to a dual-level regulation of Vbus (e.g., as depictedin FIG. 6).

Referring next to FIG. 8, shown is a block diagram depicting anotherembodiment of the present invention. As depicted, a switch-mode powersupply 806 is coupled to a controller 812, an ion-energy controlcomponent 820, and a substrate support 808 via an arc detectioncomponent 822. The controller 812, switch-mode supply 806, and ionenergy control component 820 collectively operate to apply power to thesubstrate support 808 so as to effectuate, on a time-averaged basis, adesired ion energy distribution at the surface of the substrate 810.

Referring briefly to FIG. 9A for example, shown is a periodic voltagefunction with a frequency of about 400 kHz that is modulated by asinusoidal modulating function of about 5 kHz over multiple cycles ofthe periodic voltage function. FIG. 9B is an exploded view of theportion of the periodic voltage function that is circled in FIG. 9A, andFIG. 9C depicts the resulting distribution of ion energies, on atime-averaged basis, that results from the sinusoidal modulation of theperiodic voltage function. And FIG. 9D depicts actual, direct, ionenergy measurements made in a plasma of a resultant, time-averaged, IEDFwhen a periodic voltage function is modulated by a sinusoidal modulatingfunction. As discussed further herein, achieving a desired ion energydistribution, on a time-averaged basis, may be achieved by simplychanging the modulating function that is applied to the periodicvoltage.

Referring to FIGS. 10A and 10B as another example, a 400 kHz periodicvoltage function is modulated by a sawtooth modulating function ofapproximately 5 kHz to arrive at the distribution of ion energiesdepicted in FIG. 10C on a time-averaged basis. As depicted, the periodicvoltage function utilized in connection with FIG. 10 is the same as inFIG. 9, except that the periodic voltage function in FIG. 10 ismodulated by a sawtooth function instead of a sinusoidal function.

It should be recognized that the ion energy distribution functionsdepicted in FIGS. 9C and 10C do not represent an instantaneousdistribution of ion energies at the surface of the substrate 810, butinstead represent the time average of the ion energies. With referenceto FIG. 9C, for example, at a particular instant in time, thedistribution of ion energies will be a subset of the depicteddistribution of ion energies that exist over the course of a full cycleof the modulating function.

It should also be recognized that the modulating function need not be afixed function nor need it be a fixed frequency. In some instances forexample, it may be desirable to modulate the periodic voltage functionwith one or more cycles of a particular modulating function toeffectuate a particular, time-averaged ion energy distribution, and thenmodulate the periodic voltage function with one or more cycles ofanother modulating function to effectuate another, time-averaged ionenergy distribution. Such changes to the modulating function (whichmodulates the periodic voltage function) may be beneficial in manyinstances. For example, if a particular distribution of ion energies isneeded to etch a particular geometric construct or to etch through aparticular material, a first modulating function may be used, and thenanother modulating function may subsequently be used to effectuate adifferent etch geometry or to etch through another material.

Similarly, the periodic voltage function (e.g., the 400 kHz componentsin FIGS. 9A, 9B, 10A, and 10B and Vout in FIG. 4) need not be rigidlyfixed (e.g., the shape and frequency of the periodic voltage functionmay vary), but generally its frequency is established by the transittime of ions within the chamber so that ions in the chamber are affectedby the voltage that is applied to the substrate 810.

Referring back to FIG. 8, the controller 812 provides drive-controlsignals 832′, 832″ to the switch-mode supply 806 so that the switch-modesupply 806 generates a periodic voltage function. The switch mode supply806 may be realized by the components depicted in FIG. 3 (e.g., tocreate a periodic voltage function depicted in FIG. 4), but it iscertainly contemplated that other switching architectures may beutilized.

In general, the ion energy control component 820 functions to apply amodulating function to the periodic voltage function (that is generatedby the controller 812 in connection with the switch mode power supply806). As shown in FIG. 8, the ion energy control component 820 includesa modulation controller 840 that is in communication with a custom IEDFportion 850, an IEDF function memory 848, a user interface 846, and apower component 844. It should be recognized that the depiction of thesecomponents is intended to convey functional components, which inreality, may be effectuated by common or disparate components.

The modulation controller 840 in this embodiment generally controls thepower component 844 (and hence its output 834) based upon data thatdefines a modulation function, and the power component 844 generates themodulation function 834 (based upon a control signal 842 from themodulation controller 840) that is applied to the periodic voltagefunction that is generated by the switch-mode supply 806. The userinterface 846 in this embodiment is configured to enable a user toselect a predefined IEDF function that is stored in the IEDF functionmemory 848, or in connection with the custom IEDF component 850, definea custom IEDF

In many implementations, the power component 844 includes a DC powersupply (e.g., a DC switch mode power supply or a linear amplifier),which applies the modulating function (e.g. a varying DC voltage) to theswitch mode power supply (e.g., to Vbus of the switch mode power supplydepicted in FIG. 3). In these implementations, the modulation controller840 controls the voltage level that is output by the power component 844so that the power component 844 applies a voltage that conforms to themodulating function.

In some implementations, the IEDF function memory 848 includes aplurality of data sets that correspond to each of a plurality of IEDFdistribution functions, and the user interface 846 enables a user toselect a desired IEDF function. Referring to FIG. 11 for example, shownin the right column are exemplary IEDF functions that may be availablefor a user to select. And the left column depicts the associatedmodulating function that the modulation controller 840 in connectionwith the power component 844 would apply to the periodic voltagefunction to effectuate the corresponding IEDF function. It should berecognized that the IEDF functions depicted in FIG. 11 are onlyexemplary and that other IEDF functions may be available for selection.

The custom IEDF component 850 generally functions to enable a user, viathe user interface 846, to define a desired ion energy distributionfunction. In some implementations for example, the custom IEDF component850 enables a user to establish values for particular parameters thatdefine a distribution of ion energies.

For example, the custom IEDF component 850 may enable IEDF functions tobe defined in terms of a relative level of flux (e.g., in terms of apercentage of flux) at a high-level (IF-high), a mid-level (IF-mid), anda low level (IF-low) in connection with a function(s) that defines theIEDF between these energy levels. In many instances, only IF-high,IF-low, and the IEDF function between these levels is sufficient todefine an IEDF function. As a specific example, a user may request 1200eV at a 20% contribution level (contribution to the overall IEDF), 700eV at a 30% contribution level with a sinusoid IEDF between these twolevels.

It is also contemplated that the custom IEDF portion 850 may enable auser to populate a table with a listing of one or more (e.g., multiple)energy levels and the corresponding percentage contribution of eachenergy level to the IEDF. And in yet alternative embodiments, it iscontemplated that the custom IEDF component 850 in connection with theuser interface 846 enables a user to graphically generate a desired IEDFby presenting the user with a graphical tool that enables a user to drawa desired IEDF.

In addition, it is also contemplated that the IEDF function memory 848and the custom IEDF component 850 may interoperate to enable a user toselect a predefined IEDF function and then alter the predefined IEDFfunction so as to produce a custom IEDF function that is derived fromthe predefined IEDF function.

Once an IEDF function is defined, the modulation controller 840translates data that defines the desired IEDF function into a controlsignal 842, which controls the power component 844 so that the powercomponent 844 effectuates the modulation function that corresponds tothe desired IEDF. For example, the control signal 842 controls the powercomponent 844 so that the power component 844 outputs a voltage that isdefined by the modulating function.

Referring next to FIG. 12, it is a block diagram depicting an embodimentin which an ion current compensation component 1260 compensates for ioncurrent in the plasma chamber 1204. Applicants have found that, athigher energy levels, higher levels of ion current within the chamberaffect the voltage at the surface of the substrate, and as aconsequence, the ion energy distribution is also affected. Referringbriefly to FIGS. 15A-15C for example, shown are voltage waveforms asthey appear at the surface of the substrate 1210 or wafer and theirrelationship to IEDF.

More specifically, FIG. 15A depicts a periodic voltage function at thesurface of the substrate 1210 when ion current I_(I) is equal tocompensation current Ic; FIG. 15B depicts the voltage waveform at thesurface of the substrate 1210 when ion current I_(I) is greater than thecompensation current Ic; and FIG. 15C depicts the voltage waveform atthe surface of the substrate when ion current is less than thecompensation current Ic.

As depicted in FIG. 15A, when I_(I)=Ic a spread of ion energies 1470 isrelatively narrow as compared to a uniform spread 1472 of ion energieswhen I_(I)>Ic as depicted in FIG. 15B or a uniform spread 1474 of ionenergies when I_(I)<Ic as depicted in FIG. 15C. Thus, the ion currentcompensation component 1260 enables a narrow spread of ion energies whenthe ion current is high (e.g., by compensating for effects of ioncurrent), and it also enables a width of the spread 1572, 1574 ofuniform ion energy to be controlled (e.g., when it is desirable to havea spread of ion energies).

As depicted in FIG. 15B, without ion current compensation (whenI_(I)>Ic) the voltage at the surface of the substrate, between thepositive portions of the periodic voltage function, becomes lessnegative in a ramp-like manner, which produces a broader spread 1572 ofion energies. Similarly, when ion current compensation is utilized toincrease a level of compensation current to a level that exceeds the ioncurrent (I_(I)<Ic) as depicted in FIG. 15C, the voltage at the surfaceof the substrate becomes more negative in a ramp-like manner between thepositive portions of the periodic voltage function, and a broader spread1574 of uniform ion energies is produced.

Referring back to FIG. 12, the ion compensation component 1260 may berealized as a separate accessory that may optionally be added to theswitch mode power supply 1206 and controller 1212. In other embodiments,(e.g., as depicted in FIG. 13) the ion current compensation component1260 may share a common housing 1366 with other components describedherein (e.g., the switch-mode power supply 106, 206, 806, 1206 and ionenergy control 220, 820 components).

As depicted in FIG. 13, shown is an exemplary ion current compensationcomponent 1360 that includes a current source 1364 coupled to an output1336 of a switch mode supply and a current controller 1362 that iscoupled to both the current source 1364 and the output 1336. Alsodepicted in FIG. 13 is a plasma chamber 1304, and within the plasmachamber are capacitive elements C₁, C₂, and ion current I_(I). Asdepicted, C₁ represents the inherent capacitance of componentsassociated with the chamber 1304, which may include insulation, thesubstrate, substrate support, and an echuck, and C₂ represents sheathcapacitance and stray capacitances.

It should be noted that because C₁ in this embodiment is an inherentcapacitance of components associated with the chamber 1304, it is not anaccessible capacitance that is added to gain control of processing. Forexample, some prior art approaches that utilize a linear amplifiercouple bias power to the substrate with a blocking capacitor, and thenutilize a monitored voltage across the blocking capacitor as feedback tocontrol their linear amplifier. Although a capacitor could couple aswitch mode power supply to a substrate support in many of theembodiments disclosed herein, it is unnecessary to do so becausefeedback control using a blocking capacitor is not required in severalembodiments of the present invention.

While referring to FIG. 13, simultaneous reference is made to FIG. 14,which is a graph depicting an exemplary voltage at Vo depicted in FIG.13. In operation, the current controller 1362 monitors the voltage atVo, and ion current is calculated over an interval t (depicted in FIG.14) as:

$I_{I} = {C_{1}\frac{\mathbb{d}{Vo}}{\mathbb{d}t}}$

Because C₁ is substantially constant for a given tool and is measurable,only Vo needs to be monitored to enable ongoing control of compensationcurrent. As discussed above, to obtain a more mono-energeticdistribution of ion energy (e.g., as depicted in FIG. 15A) the currentcontroller controls the current source 1364 so that Ic is substantiallythe same as I_(I). In this way, a narrow spread of ion energies may bemaintained even when the ion current reaches a level that affects thevoltage at the surface of the substrate. And in addition, if desired,the spread of the ion energy may be controlled as depicted in FIGS. 15Band 15C so that additional ion energies are realized at the surface ofthe substrate.

Also depicted in FIG. 13 is a feedback line 1370, which may be utilizedin connection with controlling an ion energy distribution. For example,the value of ΔV depicted in FIG. 14, is indicative of instantaneous ionenergy and may be used in many embodiments as part of a feedback controlloop.

Referring next to FIG. 16, shown is an exemplary embodiment of a currentsource 1664, which may be implemented to realize the current source 1364described with reference to FIG. 13. In this embodiment, a controllablenegative DC voltage source, in connection with a series inductor L2,function as a current source, but one of ordinary skill in the art willappreciate, in light of this specification, that a current source may berealized by other components and/or configurations.

Referring next to FIGS. 17A and 17B, shown are block diagrams depictingother embodiments of the present invention. As shown, the substratesupport 1708 in these embodiments includes an electrostatic chuck 1782,and an electrostatic chuck supply 1780 is utilized to apply power to theelectrostatic chuck 1782. In some variations, as depicted in FIG. 17A,the electrostatic chuck supply 1780 is positioned to apply powerdirectly to the substrate support 1708, and in other variations, theelectrostatic chuck supply 1780 is positioned to apply power inconnection with the switch mode power supply. It should be noted thatserial chucking can be carried by either a separate supply or by use ofthe controller to effect a net DC chucking function. In this DC-coupled(e.g., no blocking capacitor), series chucking function, the undesiredinterference with other RF sources can be minimized.

Shown in FIG. 18 is a block diagram depicting yet another embodiment ofthe present invention in which a plasma power supply 1884 that generallyfunctions to generate plasma density is also configured to drive thesubstrate support 1808 alongside the switch mode power supply 1806 andelectrostatic chuck supply 1880. In this implementation, each of theplasma power supply 1884, the electrostatic chuck supply 1880, and theswitch mode power supply 1806 may reside in separate assemblies, or twoor more of the supplies 1806, 1880, 1884 may be architected to reside inthe same physical assembly. Beneficially, the embodiment depicted inFIG. 18 enables a top electrode 1886 (e.g., shower head) to beelectrically grounded so as to obtain electrical symmetry and reducedlevel of damage due to fewer arcing events.

Referring to FIG. 19, shown is a block diagram depicting still anotherembodiment of the present invention. As depicted, the switch mode powersupply 1906 in this embodiment is configured to apply power to thesubstrate support and the chamber 1904 so as to both bias the substrateand ignite (and sustain) the plasma without the need for an additionalplasma power supply (e.g., without the plasma power supply 102, 202,1202, 1702, 1884). For example, the switch-mode power supply 1806 may beoperated at a duty cycle that is sufficient to ignite and sustain theplasma while providing a bias to the substrate support.

Referring next to FIG. 20, it is a block diagram depicting inputparameters and control outputs of a control portion that may be utilizedin connection with the embodiments described with reference to FIGS.1-19. The depiction of the control portion is intended to provide asimplified depiction of exemplary control inputs and outputs that may beutilized in connection with the embodiments discussed herein—it is notintended to a be hardware diagram. In actual implementation, thedepicted control portion may be distributed among several discretecomponents that may be realized by hardware, software, firmware, or acombination thereof.

With reference to the embodiments previously discussed herein, thecontroller depicted in FIG. 20 may provide the functionality of one ormore of the controller 112 described with reference to FIG. 1; thecontroller 212 and ion energy control 220 components described withreference to FIG. 2; the controller 812 and ion energy control portion820 described with reference to FIG. 8; the ion compensation component1260 described with reference to FIG. 12; the current controller 1362described with reference to FIG. 13; the Icc control depicted in FIG.16, controllers 1712A, 1712B depicted in FIGS. 17A and 17B,respectively; and controllers 1812, 1912 depicted in FIGS. 18 and 19,respectively.

As shown, the parameters that may be utilized as inputs to the controlportion include dVo/dt and ΔV, which are described in more detail withreference to FIGS. 13 and 14. As discussed, dVo/dt may be utilized to inconnection with an ion-energy-distribution-spread input ΔE to provide acontrol signal Icc, which controls a width of the ion energydistribution spread as described with reference to FIGS. 12, 13, 14,15A-C, and FIG. 16. In addition, an ion energy control input (Ei) inconnection with optional feedback ΔV may be utilized to generate an ionenergy control signal (e.g., that affects Vbus depicted in FIG. 3) toeffectuate a desired ion energy distribution as described in more detailwith reference to FIGS. 1-11. And another parameter that may be utilizedin connection with many e-chucking embodiments is a DC offset input,which provides electrostatic force to hold the wafer to the chuck forefficient thermal control.

FIG. 21 illustrates a plasma processing system 2100 according to anembodiment of this disclosure. The system 2100 includes a plasmaprocessing chamber 2102 enclosing a plasma 2104 for etching a topsurface 2118 of a substrate 2106. The plasma is generated by a plasmasource 2112 (e.g., in-situ or remote or projected) powered by a plasmapower supply 2122. A plasma sheath voltage V_(sheath) measured betweenthe plasma 2104 and the top surface 2118 of the substrate 2106accelerates ions from the plasma 2104 across a plasma sheath 2115,causing the accelerated ions to impact a top surface 2118 of a substrate2106 and etch the substrate 2106 (or portions of the substrate 2106 notprotected by photoresist). The plasma 2104 is at a plasma potential V₃relative to ground (e.g., the plasma processing chamber 2102 walls). Thesubstrate 2106 has a bottom surface 2120 that is electrostatically heldto a support 2108 via an electrostatic chuck 2111 and a chuckingpotential V_(chuck) between a top surface 2121 of the electrostaticchuck 2111 and the substrate 2106. The substrate 2106 is dielectric andtherefore can have a first potential V₁ at the top surface 2118 and asecond potential V₂ at the bottom surface 2120. The top surface of theelectrostatic chuck 2121 is in contact with the bottom surface 2120 ofthe substrate, and thus these two surfaces 2120, 2121 are at the samepotential, V₂. The first potential V₁, the chucking potential V_(chuck),and the second potential V₂, are controlled via an AC waveform with a DCbias or offset generated by a switch mode power supply 2130 and providedto the electrostatic chuck 2111 via a first conductor 2124. Optionally,the AC waveform is provided via the first conductor 2124, and the DCwaveform is provided via an optional second conductor 2125. The AC andDC output of the switch mode power supply 2130 can be controlled via acontroller 2132, which is also configured to control various aspects ofthe switch mode power supply 2130.

Ion energy and ion energy distribution are a function of the firstpotential V₁. The switch mode power supply 2130 provides an AC waveformtailored to effect a desired first potential V₁ known to generate adesired ion energy and ion energy distribution. The AC waveform can beRF and have a non-sinusoidal waveform such as that illustrated in FIGS.5, 6, 11, 14, 15 a, 15 b, and 15 c. The first potential V₁ can beproportional to the change in voltage ΔV illustrated in FIG. 14. Thefirst potential V₁ is also equal to the plasma voltage V₃ minus theplasma sheath voltage V_(sheath). But since the plasma voltage V₃ isoften small (e.g., less than 20 V) compared to the plasma sheath voltageV_(sheath) (e.g., 50 V-2000 V), the first potential V₁ and the plasmasheath voltage V_(sheath) are approximately equal and for purposes ofimplementation can be treated as being equal. Thus, since the plasmasheath voltage V_(sheath) dictates ion energies, the first potential V₁is proportional to ion energy distribution. By maintaining a constantfirst potential V₁, the plasma sheath voltage V_(sheath) is constant,and thus substantially all ions are accelerated via the same energy, andhence a narrow ion energy distribution is achieved. The plasma voltageV₃ results from energy imparted to the plasma 2104 via the plasma source2112. The first potential V₁ at the top surface 2118 of the substrate2106 is formed via a combination of capacitive charging from theelectrostatic chuck 2111 and charge buildup from electrons and ionspassing through the sheath 2115. The AC waveform from the switch modepower supply 2130 is tailored to offset the effects of ion and electrontransfer through the sheath 2115 and the resulting charge buildup at thetop surface 2118 of the substrate 2106 such that the first potential V₁remains substantially constant.

The chucking force that holds the substrate 2106 to the electrostaticchuck 2111 is a function of the chucking potential V_(chuck). The switchmode power supply 2130 provides a DC bias, or DC offset, to the ACwaveform, so that the second potential V₂ is at a different potentialthan the first potential V₁. This potential difference causes thechucking voltage V_(chuck). The chucking voltage V_(chuck) can bemeasured from the top surface 2221 of the electrostatic chuck 2111 to areference layer inside the substrate 2106, where the reference layerincludes any elevation inside the substrate except a bottom surface 2120of the substrate 2106 (the exact location within the substrate 2106 ofthe reference layer can vary). Thus, chucking is controlled by and isproportional to the second potential V₂.

In an embodiment, the second potential V₂ is equal to the DC offset ofthe switch mode power supply 2130 modified by the AC waveform (in otherwords an AC waveform with a DC offset where the DC offset is greaterthan a peak-to-peak voltage of the AC waveform). The DC offset may besubstantially larger than the AC waveform, such that the DC component ofthe switch mode power supply 2130 output dominates the second potentialV₂ and the AC component can be neglected or ignored.

The potential within the substrate 2106 varies between the first andsecond potentials V₁, V₂. The chucking potential V_(chuck) can bepositive or negative (e.g., V₁>V₂ or V₁<V₂) since the coulombicattractive force between the substrate 2106 and the electrostatic chuck2111 exists regardless of the chucking potential V_(chuck) polarity.

The switch mode power supply 2130 in conjunction with the controller2132 can monitor various voltages deterministically and without sensors.In particular, the ion energy (e.g., mean energy and ion energydistribution) is deterministically monitored based on parameters of theAC waveform (e.g., slope and step). For instance, the plasma voltage V₃,ion energy, and ion energy distribution are proportional to parametersof the AC waveform produced by the switch mode power supply 2130. Inparticular the ΔV of the falling edge of the AC waveform (see forexample FIG. 14), is proportional to the first potential V₁, and thus tothe ion energy. By keeping the first potential V₁ constant, the ionenergy distribution can be dept narrow.

Although the first potential V₁ cannot be directly measured and thecorrelation between the switch mode power supply output and the firstvoltage V₁ may vary based on the capacitance of the substrate 2106 andprocessing parameters, a constant of proportionality between ΔV and thefirst potential V₁ can be empirically determined after a shortprocessing time has elapsed. For instance, where the falling edge ΔV ofthe AC waveform is 50 V, and the constant of proportionality isempirically found to be 2 for the given substrate and process, the firstpotential V₁ can be expected to be 100 V. Thus, the first potential V₁,along with ion energy, and ion energy distribution can be determinedbased on knowledge of the AC waveform of the switch mode power supplywithout any sensors inside the plasma processing chamber 2102.Additionally, the switch mode power supply 2130 in conjunction with thecontroller 2132 can monitor when and if chucking is taking place (e.g.,whether the substrate 2106 is being held to the electrostatic chuck 2111via the chucking potential V_(chuck)).

Dechucking is performed by eliminating or decreasing the chuckingpotential V_(chuck). This can be done by setting the second potential V₂equal to the first potential V₁. In other words, the DC offset and theAC waveform can be adjusted in order to cause the chucking voltageV_(chuck) to approach 0 V. Compared to conventional dechucking methods,the system 2100 achieves faster dechucking and thus greater throughputsince both the DC offset and the AC waveform can be adjusted to achievedechucking. Also, when the DC and AC power supplies are in the switchmode power supply 2130, their circuitry is more unified, closertogether, can be controlled via a single controller 2132 (as compared totypical parallel arrangements of DC and AC power supplies), and changeoutput faster. The speed of dechucking enabled by the embodiments hereindisclosed also enables dechucking after the plasma 2104 is extinguished,or at least after power from the plasma source 2112 has been turned off.

The plasma source 2112 can take a variety of forms. For instance, in anembodiment, the plasma source 2112 includes an electrode inside theplasma processing chamber 2102 that establishes an RF field within thechamber 2102 that both ignites and sustains the plasma 2104. In anotherembodiment, the plasma source 2112 includes a remote projected plasmasource that remotely generates an ionizing electromagnetic field,projects or extends the ionizing electromagnetic field into theprocessing chamber 2102, and both ignites and sustains the plasma 2104within the plasma processing chamber using the ionizing electromagneticfield. Yet, the remote projected plasma source also includes a fieldtransfer portion (e.g., a conductive tube) that the ionizingelectromagnetic field passes through en route to the plasma processingchamber 2102, during which time the ionizing electromagnetic field isattenuated such that the field strength within the plasma processingchamber 2102 is only a tenth or a hundred or a thousandth or an evensmaller portion of the field strength when the field is first generatedin the remote projected plasma source. The plasma source 2112 is notdrawn to scale.

The switch mode power supply 2130 can float and thus can be biased atany DC offset by a DC power source (not illustrated) connected in seriesbetween ground and the switch mode power supply 2130. The switch modepower supply 2130 can provide an AC waveform with a DC offset either viaAC and DC power sources internal to the switch mode power supply 2130(see for example FIGS. 22, 23, 26), or via an AC power source internalto the switch mode power supply 2130 and a DC power supply external tothe switch mode power supply 2130 (see for example FIGS. 24, 27). In anembodiment, the switch mode power supply 2130 can be grounded and beseries coupled to a floating DC power source coupled in series betweenthe switch mode power supply 2130 and the electrostatic chuck 2111.

The controller 2132 can control an AC and DC output of the switch modepower supply when the switch mode power supply 2130 includes both an ACand DC power source. When the switch mode power supply 2130 is connectedin series with a DC power source, the controller 2132 may only controlthe AC output of the switch mode power supply 2130. In an alternativeembodiment, the controller 2130 can control both a DC power supplycoupled to the switch mode power supply 2130, and the switch mode powersupply 2130. One skilled in the art will recognize that while a singlecontroller 2132 is illustrated, other controllers can also beimplemented to control the AC waveform and DC offset provided to theelectrostatic chuck 2111.

The electrostatic chuck 2111 can be a dielectric (e.g., ceramic) andthus substantially block passage of DC voltages, or it can be asemiconductive material such as a doped ceramic. In either case, theelectrostatic chuck 2111 can have a second voltage V₂ on a top surface2121 of the electrostatic chuck 2111 that capacitively couples voltageto a top surface 2118 of the substrate 2106 (usually a dielectric) toform the first voltage V₁.

The plasma 2104 shape and size are not necessarily drawn to scale. Forinstance, an edge of the plasma 2104 can be defined by a certain plasmadensity in which case the illustrated plasma 2104 is not drawn with anyparticular plasma density in mind. Similarly, at least some plasmadensity fills the entire plasma processing chamber 2102 despite theillustrated plasma 2104 shape. The illustrated plasma 2104 shape isintended primarily to show the sheath 2115, which does have asubstantially smaller plasma density than the plasma 2104.

FIG. 22 illustrates another embodiment of a plasma processing system2200. In the illustrated embodiment, the switch mode power supply 2230includes a DC power source 2234 and an AC power source 2236 connected inseries. Controller 2232 is configured to control an AC waveform with aDC offset output of the switch mode power supply 2230 by controllingboth the AC power source 2236 waveform and the DC power source 2234 biasor offset. This embodiment also includes an electrostatic chuck 2211having a grid or mesh electrode 2210 embedded in the chuck 2211. Theswitch mode power supply 2230 provides both an AC and DC bias to thegrid electrode 2210. The DC bias along with the AC component, which issubstantially smaller than the DC bias and can thus be neglected,establishes a third potential V₄ on the grid electrode 2210. When thethird potential V₄ is different than a potential at a reference layeranywhere within the substrate 2206 (excluding the bottom surface 2220 ofthe substrate 2206), a chucking potential V_(chuck) and a coulombicchucking force are established which hold the substrate 2206 to theelectrostatic chuck 2211. The reference layer is an imaginary planeparallel to the grid electrode 2210. The AC waveform capacitivelycouples from the grid electrode 2210 through a portion of theelectrostatic chuck 2211, and through the substrate 2206 to control thefirst potential V₁ on a top surface 2218 of the substrate 2206. Since aplasma potential V₃ is negligible relative to a plasma sheath voltageV_(sheath), the first potential V₁ and the plasma sheath voltageV_(sheath) are approximately equal, and for practical purposes areconsidered equal. Therefore, the first potential V₁ equals the potentialused to accelerate ions through the sheath 2215.

In an embodiment, the electrostatic chuck 2211 can be doped so as to beconductive enough that any potential difference through the body of thechuck 2211 is negligible, and thus the grid or mesh electrode 2210 canbe at substantially the same voltage as the second potential V₂.

The grid electrode 2210 can be any conductive planar device embedded inthe electrostatic chuck 2211, parallel to the substrate 2206, andconfigured to be biased by the switch mode power supply 2230 and toestablish a chucking potential V_(chuck). Although the grid electrode2210 is illustrated as being embedded in a lower portion of theelectrostatic chuck 2211, the grid electrode 2210 can be located closeror further from the substrate 2206. The grid electrode 2210 also doesnot have to have a grid pattern. In an embodiment, the grid electrode2210 can be a solid electrode or have a non-solid structure with anon-grid shape (e.g., a checkerboard pattern). In an embodiment, theelectrostatic chuck 2211 is a ceramic or other dielectric and thus thethird potential V₄ on the grid electrode 2210 is not equal to the firstpotential V₁ on a top surface 2221 of the electrostatic chuck 2211. Inanother embodiment, the electrostatic chuck 2211 is a doped ceramic thatis slightly conductive and thus the third potential V₄ on the gridelectrode 2210 can be equal to the second potential V₂ on the topsurface 2221 of the electrostatic chuck 2211.

The switch mode power supply 2230 generates an AC output that can benon-sinusoidal. The switch mode power supply 2230 is able to operate theDC and AC sources 2234, 2236 in series because the DC power source 2234is AC-conductive and the AC power source 2236 is DC-conductive.Exemplary AC power sources that are not DC-conductive are certain linearamplifiers which can be damaged when provided with DC voltage orcurrent. The use of AC-conductive and DC-conductive power sourcesreduces the number of components used in the switch mode power supply2230. For instance, if the DC power source 2234 is AC-blocking, then anAC-bypass or DC-blocking component (e.g., a capacitor) may have to bearranged in parallel with the DC power source 2234. If the AC powersource 2236 is DC-blocking, then a DC-bypass or AC-blocking component(e.g., an inductor) may have to be arranged in parallel with the ACpower source 2236.

In this embodiment, the AC power source 2238 is generally configured toapply a voltage bias to the electrostatic chuck 2211 in a controllablemanner so as to effectuate a desired ion energy distribution for theions bombarding the top surface 2218 of the substrate 2206. Morespecifically, the AC power source 2236 is configured to effectuate thedesired ion energy distribution by applying one or more particularwaveforms at particular power levels to the grid electrode 2210. Andmore particularly, the AC power source 2236 applies particular powerlevels to effectuate particular ion energies, and applies the particularpower levels using one or more voltage waveforms defined by waveformdata stored in a waveform memory (not illustrated). As a consequence,one or more particular ion bombardment energies may be selected to carryout controlled etching of the substrate 2206. In one embodiment, the ACpower source 2236 can make use of a switched mode configuration (see forexample FIGS. 25-27). The switch mode power supply 2230, andparticularly the AC power source 2236, can produce an AC waveform asdescribed in various embodiments of this disclosure.

One skilled in the art will recognize that the grid electrode 2210 maynot be necessary and that other embodiments can be implemented withoutthe grid electrode 2210. One skilled in the art will also recognize thatthe grid electrode 2210 is just one example of numerous devices that canbe used to establish chucking potential V_(chuck).

FIG. 23 illustrates another embodiment, of a plasma processing system2300. The illustrated embodiment includes a switch mode power supply2330 for providing an AC waveform and a DC bias to an electrostaticchuck 2311. The switch mode power supply 2330 includes a DC power source2334 and an AC power source 2336, both of which can be grounded. The ACpower source 2336 generates an AC waveform that is provided to a firstgrid or mesh electrode 2310 embedded in the electrostatic chuck 2311 viaa first conductor 2324. The AC power source 2336 establishes a potentialV₄ on the first grid or mesh electrode 2310. The DC power source 2334generates a DC bias that is provided to a second grid or mesh electrode2312 embedded in the electrostatic chuck 2311 via a second conductor2325. The DC power source 2334 establishes a potential V₅ on the secondgrid or mesh electrode 2312. The potentials V₄ and V₅ can beindependently controlled via the AC and DC power sources 2336, 2334,respectively. However, the first and second grid or mesh electrodes2310, 2312 can also be capacitively coupled and/or there can be DCcoupling between the grid or mesh electrodes 2310, 2312 via a portion ofthe electrostatic chuck 2311. If either AC or DC coupling exists, thenthe potentials V₄ and V₅ may be coupled. One skilled in the art willrecognize that the first and second grid electrodes 2310, 2312 can bearranged in various locations throughout the electrostatic chuck 2311including arranging the first grid electrode 2310 closer to thesubstrate 2306 than the second grid electrode 2312.

FIG. 24 illustrates another embodiment of a plasma processing system2400. In this embodiment, a switch mode power supply 2430 provides an ACwaveform to an electrostatic chuck 2411, where the switch mode powersupply 2430 output is offset by a DC bias provided by a DC power supply2434. The AC waveform of the switch mode power supply 2430 has awaveform selected by controller 2435 to bombard a substrate 2406 withions from a plasma 2404 having a narrow ion energy distribution. The ACwaveform can be non-sinusoidal (e.g., square wave or pulsed) and can begenerated via an AC power source 2436 of the switch mode power supply2430. Chucking is controlled via the DC offset from the DC power supply2434, which is controlled by controller 2433. The DC power supply 2434can be coupled in series between ground and the switch mode power supply2430. The switch mode power supply 2430 is floating such that its DCbias can be set by the DC power supply 2434.

One skilled in the art will recognize that while the illustratedembodiment shows two independent controllers 2433, 2435, these could becombined into a single functional unit, device, or system such asoptional controller 2432. Additionally, controllers 2433 and 2435 can becoupled so as to communicate with each other and share processingresources.

FIG. 25 illustrates a further embodiment of a plasma processing system2500. The illustrated embodiment includes a switch mode power supply2530 that produces an AC waveform that can have a DC offset provided bya DC power supply (not illustrated). The switch mode power supply can becontrolled via optional controller 2535, which encompasses a voltage andcurrent controller 2537, 2539. The switch mode power supply 2530 caninclude a controllable voltage source 2538 having a voltage outputcontrolled by the voltage controller 2537, and a controllable currentsource 2540 having a current output controlled by the current controller2539. The controllable voltage and current sources 2538, 2540 can be ina parallel arrangement. The controllable current source 2540 isconfigured to compensate for an ion current between a plasma 2504 and asubstrate 2506.

The voltage and current controllers 2537, 2539 can be coupled and incommunication with each other. The voltage controller 2537 can alsocontrol a switched output 2539 of the controllable voltage source 2538.The switched output 2539 can include two switches in parallel asillustrated, or can include any circuitry that converts an output of thecontrollable voltage source 2538 into a desired AC waveform (e.g.,non-sinusoidal). Via the two switches, a controlled voltage or ACwaveform from the controllable voltage source 2538 can be combined witha controlled current output of the controllable current source 2540 togenerate an AC waveform output of the switch mode power supply 2530.

The controllable voltage source 2538 is illustrated as having a givenpolarity, but one skilled in the art will recognize that the oppositepolarity is an equivalent to that illustrated. Optionally, thecontrollable voltage and current sources 2538, 2540 along with theswitched output 2539 can be part of an AC power source 2536 and the ACpower source 2536 can be arranged in series with a DC power source (notillustrated) that is inside or outside of the switch mode power supply2530.

FIG. 26 illustrates yet another embodiment of a plasma processing system2600. In the illustrated embodiment, a switch mode power supply 2630provides an AC waveform having a DC offset to an electrostatic chuck2611. The AC component of the waveform is generated via a parallelcombination of a controllable voltage source 2638 and a controllablecurrent source 2640 connected to each other through a switched output2639. The DC offset is generated by a DC power source 2634 coupled inseries between ground and the controllable voltage source 2638. In anembodiment, the DC power source 2634 can be floating rather thangrounded. Similarly, the switch mode power supply 2630 can be floatingor grounded.

The system 2600 can include one or more controllers for controlling anoutput of the switch mode power supply 2630. A first controller 2632 cancontrol the output of the switch mode power supply 2630, for instancevia a second controller 2633 and a third controller 2635. The secondcontroller 2633 can control a DC offset of the switch mode power supply2630 as generated by the DC power source 2634. The third controller 2635can control the AC waveform of the switch mode power supply 2630 bycontrolling the controllable voltage source 2638 and the controllablecurrent source 2640. In an embodiment, a voltage controller 2637controls the voltage output of the controllable voltage source 2638 anda current controller 2639 controls a current of the controllable currentsource 2640. The voltage and current controllers 2637, 2639 can be incommunication with each other and can be a part of the third controller2635.

One skilled in the art will recognize that the embodiments above,describing various configurations of controllers relative to the powersources 2634, 2638, 2640, are not limiting, and that various otherconfigurations can also be implemented without departing from thisdisclosure. For instance, the third controller 2635 or the voltagecontroller 2637 can control a switched output 2639 between thecontrollable voltage source 2638 and the controllable current source2640. As another example, the second and third controllers 2633, 2635can be in communication with each other (even though not illustrated assuch). It should also be understood that the polarities of thecontrollable voltage and current sources 2638, 2640 are illustrativeonly and not meant to be limiting.

The switched output 2639 can operate by alternately switching twoparallel switches in order to shape an AC waveform. The switched output2639 can include any variety of switches including, but not limited to,MOSFET and BJT. In one variation, the DC power source 2634 can bearranged between the controllable current source 2640 and theelectrostatic chuck 2611 (in other words, the DC power source 2634 canfloat), and the switch mode power supply 2630 can be grounded.

FIG. 27 illustrates another embodiment of a plasma processing system2700. In this variation, the switch mode power supply 2734 again isgrounded, but instead of being incorporated into the switch mode powersupply 2730, here the DC power source 2734 is a separate component andprovides a DC offset to the entire switch mode power supply 2730 ratherthan just components within the switch mode power supply 2730.

FIG. 28 illustrates a method 2800 according to an embodiment of thisdisclosure. The method 2800 includes a place a substrate in a plasmachamber operation 2802. The method 2800 further includes a form a plasmain the plasma chamber operation 2804. Such a plasma can be formed insitu or via a remote projected source. The method 2800 also includes aswitch power operation 2806. The switch power operation 2806 involvescontrollably switching power to the substrate so as to apply a periodvoltage function to the substrate. The periodic voltage function can beconsidered a pulsed waveform (e.g., square wave) or an AC waveform andincludes a DC offset generated by a DC power source in series with aswitch mode power supply. In an embodiment, the DC power source can beincorporated into the switch mode power supply and thus be in serieswith an AC power source of the switch mode power supply. The DC offsetgenerates a potential difference between a top surface of anelectrostatic chuck and a reference layer within the substrate and thispotential difference is referred to as the chucking potential. Thechucking potential between the electrostatic chuck and the substrateholds the substrate to the electrostatic chuck thus preventing thesubstrate from moving during processing. The method 2800 furtherincludes a modulate operation 2808 in which the periodic voltagefunction is modulated over multiple cycles. The modulation is responsiveto a desired ion energy distribution at the surface of the substrate soas to effectuate the desired ion energy distribution on a time-averagedbasis.

FIG. 29 illustrates another method 2900 according to an embodiment ofthis disclosure. The method 2900 includes a place a substrate in aplasma chamber operation 2902. The method 2900 further includes a form aplasma in the plasma chamber operation 2904. Such a plasma can be formedin situ or via a remote projected source. The method 2900 also includesa receive at least one ion-energy distribution setting operation 2906.The setting received in the receive operation 2906 can be indicative ofone or more ion energies at a surface of the substrate. The method 2900further includes a switch power operation 2908 in which power to thesubstrate is controllably switched so as to effectuate the following:(1) a desired distribution of ion energies on a time-averaged basis; and(2) a desired chucking potential on a time-averaged basis. The power canhave an AC waveform and a DC offset.

In conclusion, the present invention provides, among other things, amethod and apparatus for selectively generating desired ion energiesusing a switch-mode power. Those skilled in the art can readilyrecognize that numerous variations and substitutions may be made in theinvention, its use, and its configuration to achieve substantially thesame results as achieved by the embodiments described herein.Accordingly, there is no intention to limit the invention to thedisclosed exemplary forms. Many variations, modifications, andalternative constructions fall within the scope and spirit of thedisclosed invention.

What is claimed is:
 1. A system for plasma-based processing, comprising:a plasma processing chamber configured to contain a plasma; anelectrostatic chuck positioned within the plasma processing chamber andcoupled to a substrate, an ion-energy control portion, the ion-energycontrol portion including a controllable DC voltage source to provide aDC output voltage defined by a potential difference between a firstvoltage and a ground potential, wherein the potential difference has amagnitude that is determined by at least one ion-energy distributionsetting, wherein the ion-energy distribution setting is indicative of adesired ion energy distribution of the ions at the surface of thesubstrate; a first switching component disposed to switchably couple thefirst voltage of the DC voltage source to the electrostatic chuck; asecond switching component disposed to switchably couple the groundpotential of the DC voltage source to the electrostatic chuck; a firstcontroller to alternately open and close the first and second switchingcomponents to alternately apply the first voltage and the groundpotential of the DC voltage source to the electrostatic chuck; a DCoffset supply coupled to the electrostatic chuck; a DC offset controllerto control a DC offset voltage applied by the DC offset supply; and anion current compensation component coupled to the electrostatic chuck,the ion current compensation component, including a controllable DCcurrent source coupled to the electrostatic chuck to provide anuninterrupted compensation current, which is fixed in magnitude to thesubstrate support, wherein DC power including the DC voltage source, theDC offset supply, and the DC current source is the sole source of powerapplied to the electrostatic chuck.
 2. The system of claim 1, whereinthe DC voltage source is floating.
 3. The system of claim 1, wherein thefirst and second switching components respectively couple the first andsecond voltages to the electrostatic chuck via a first conductor, andthe DC offset voltage is provided to the electrostatic chuck via asecond conductor.
 4. An apparatus for plasma-based processing,comprising: a controller configured to provide at least two separategate drive-control signals, the at least two separate gate drive controlsignals are either high or low and are not simultaneously high; a switchmode power supply adapted to provide a periodic voltage function,responsive to the at least two gate drive-control signals, to anelectrostatic chuck of a plasma processing chamber, the switch modepower supply having at least two field effect transistor (FET) switchingcomponents configured to alternately couple a DC voltage and a groundpotential to the electrostatic chuck in response to the gate drivecontrol signals to generate a pulsed voltage, each of the FET switchingcomponents including a gate disposed to receive a corresponding one ofthe at least two gate drive control signals; a DC offset supply disposedto apply a DC offset to the pulsed voltage; and a DC current sourcecoupled to the switch mode power supply, the DC current source isconfigured to provide constant uninterrupted current that is fixed inmagnitude, and the output from the DC current source is combined withthe pulsed voltage before reaching the electrostatic chuck and DC powerincluding the DC voltage, the DC offset supply, and the DC currentsource is a sole source of power output from the apparatus, and where anamplitude of the constant uninterrupted current output from the DCcurrent source controls a width of an ion energy distribution of aplasma in the plasma processing chamber.
 5. The apparatus of claim 4,wherein the switch mode power supply is floating.
 6. The apparatus ofclaim 4, wherein the pulsed voltage and the current output of the DCcurrent source are combined in parallel within the switch mode powersupply.
 7. The apparatus of claim 4, wherein the DC offset supply iscoupled in series with the switch mode power supply.
 8. The apparatus ofclaim 4, wherein the pulsed voltage from the switch mode power supplyand the current output of the DC current source are combined in paralleloutside the switch mode power supply.
 9. An apparatus for plasma-basedprocessing, comprising: a DC power supply that provides a positive DCvoltage that is fixed at a magnitude responsive to an ion-energysetting, wherein the ion-energy setting is indicative of a desired ionenergy at the surface of a substrate; an output disposed to couple to asubstrate support; two switching components including a first switchingcomponent coupled to the positive DC power supply and a second switchingcomponent coupled to a ground terminal, the two switching componentsconfigured to alternately couple the positive DC voltage and the groundterminal to the output; a DC offset supply disposed to apply a DC offsetto the output; and an ion current compensation component coupled to theoutput, the ion current compensation component including: a controllableDC current source, separate from the DC power supply, that isconsistently coupled to the output; and a current controller configuredto monitor a rate of change of a voltage of the output and maintain anuninterrupted DC current, which is fixed in magnitude, to the outputbased upon the rate of change of the voltage.
 10. The system of claim 1wherein the ion current compensation component is configured to enable auser to define a spread of a uniform distribution of ion energy.